In the commercial utilization of synthetic resin foams such as polyurethane foams, it is common to mix the reactants in a mixhead and then pass them through a nozzle into a mold having the shape of the desired end product or into a cavity which it is desired to fill with foam. The mixhead, nozzle and supply source are typically operated either as a higher pressure system at about 1000 psi or as a low pressure system at about 100 to 200 psi. After each pouring or mold filling cycle it is common to flush the nozzle. In the high pressure system this is commonly done with high pressure air (about 150 psig) alone but in the low pressure system a combination of an air flush and a solvent flush is typically employed. With many types of foam reactants these procedures have been adequate. Recently, however, very fast foam reactants have been introduced with which it is difficult to completely clear the nozzle or outlet by these flushing procedures. The air and solvent flush has had less difficulty than the air flush with these reactants but the use of solvent flushing is somewhat disfavored due to the short supply of solvent with the concurrent high cost and the safety hazards involved in solvent flushing. In fact, safety considerations preclude the use of solvent flushing in high pressure systems. In systems utilizing such reactants, it has been common to use a nozzle until it can no longer be adequately flushed. At this point, the entire nozzle assembly is removed, soaked overnight in a solvent and then cleaned with a wire brush. This procedure entails considerable labor and requires a stock of nozzle assemblies not otherwise needed.
The prior art, therefore, does not provide an easy safe and economical method of pouring very fast foaming reactants, nor does the art disclose a nozzle assembly especially adapted to the pouring of such reactants. There is no disclosure of how to use fast foaming reactants in a low pressure system without a solvent flush.